Hydrazine hydrohalogenides are industrially useful for a wide variety of applications, such as production of hydrazine, foaming agents, and the like, and, therefore, development of a process for preparing them at low cost has been demanded.
It is known that benzophenone-imines are contacted with molecular oxygen in the presence of a copper halide catalyst to obtain benzophenone-azines as described in U.S. Pat. No. 2,870,206 and that azines are hydrolyzed with an aqueous solution of a hydrohalogenic acid to obtain hydrazine hydrohalogenides as described in Japanese Patent Application (OPI) No. 97600/76 (the term "OPI" as used herein means an "unexamined published patent application").
Production of hydrazine hydrohalogenides by combining these processes is industrially advantageous but inevitably involves removal and reuse of the copper catalyst used.
Known processes for recovering the copper halide catalyst comprise adding water, aqueous ammonia or an aqueous salt solution to the reaction mixture containing the produced benzophenone-azines to precipitate the copper halide catalyst and reusing the recovered catalyst as disclosed in Japanese Patent Application (OPI) Nos. 71045/78 and 38346/80. These processes, however, cannot be considered industrially advantageous because of poor workability resulting from handling of a solid.